ptrCast to packed struct with packed sub-struct not behaving as I would expect

[loris-olsem]

Observed with latest release 0.6.0+66d76cc4f.

Please see my example below

To me it looks like that the non 16 bit aligned packed sub-struct is causing a problem here.
Writes to the interpreted pointer do not end up in the right locations in memory.
From the documentation this appeared to me the right way to do an interpret cast, or am I missing something here?

Moving all the fields of Cat (including the culprit byte) into Foo makes it behave it again as I would expect.

const std = @import("std");

const Cat = packed struct {
    culprit: u8, // comment in this field and buff will look as expected
    f1: u16,
    f2: u16,
};

const Foo = packed struct {
    cat1: Cat,
};

pub fn main () !void {
    var buff = [_]u8{0} ** (@sizeOf(Foo));
    var foo = @ptrCast(*Foo, &buff);
    foo.cat1.f1 = 0x11;
    foo.cat1.f2 = 0x22;

    var w = std.io.getStdOut().writer();
    // with culprit byte I get 2200000000000000
    // with *no* culprit byte I get, as expected, 11002200
    try w.print("{x}\n", .{buff});
}

[Vexu]

Packed structs are known to be buggy, this is likely #2627. #3133 is the tracking issue to fix them.